Pennsylvania Electrical Suppliers - #2 SER for 100A sub??

[Dennis Alwon]

What would be the reasoning for the larger wire if it doesnt carry the entire load? Also I know around here almost everyone uses #2 for "sub" subpanels

The concept is the dwelling as a whole is a very diversified load and because of this T. 310.15(B)(6) comes into play. When you change the diversity by putting different loads in different panels it supposedly no longer works. That being said there are major issues with the reasoning and concept of this article.

I bet things change the next cycle.

 

[Flex]

Thank you for clearing things up for me. I really enjoy coming on here and learning.

 

[PetrosA]

As a PA guy, I admit this seemed like a strange post to me. We never had inspection problems with #2 riser for 100A subpanels, and I'm not even sure we could get 1/0 riser that easily. The other thing I checked after reading this post were the wire capacities of a BR2100, which are maxed out at 1/0 which would mean that there's going to be a maximum distance you can run a 100A subpanel from it's OCPD with an aluminum SER (considering you can't upsize for voltage drop). Strange. I'll ask around.

 

[LarryFine]

So, have the cable manufacturers come out with new code-compliant sizes of SER for us yet?

 

[Twoskinsoneman]

So, have the cable manufacturers come out with new code-compliant sizes of SER for us yet?

With manufacturers driving the change you would think they would be ready with a new bigger more expensive cable in hand ready to sell....

 

[Dennis Alwon]

So, have the cable manufacturers come out with new code-compliant sizes of SER for us yet?

I believe southwire has made a 250 MCM ser but the fact is that it still isn't compliant. We also need the manufacturers of the panels to make the lugs bigger since most are only rated for 250MCM.

Use copper or wire in conduit and the issue is taken care of immediately. I haven't used ser or seu in 20 years for services.

 

[electricmanscott]

Use copper or wire in conduit and the issue is taken care of immediately. I haven't used ser or seu in 20 years for services.

Try explaining that new conduit running accross some ladys living room ceiling....

 

[Sierrasparky]

I've got a good one.

How about if you use one of those 200 amp resi panels that are set up for Well pumps. They have a 200 amp main breaker and a couple of spaces for the pump breakers. The buss has feed through lugs for the Main house panel.

So what size wire do we use?

2005=?

2008= ?

 

[emf10]

I've got a good one.

How about if you use one of those 200 amp resi panels that are set up for Well pumps. They have a 200 amp main breaker and a couple of spaces for the pump breakers. The buss has feed through lugs for the Main house panel.

So what size wire do we use?

2005=?

2008= ?

For 2005 I think it would require 250kcm AL SE with 75 degree terminals since the 200A feed from the main breaker to a 200A panel in the house is not the "main power feeder" (from the poco to the 200A panel with the well breakers is the main feeder and could use #4/0 AL), for 2008 it would more clearly be #350kcm AL SE since it dosen't carry all loads associated with the dwelling and SE is restricted to the 60 degree column. Seems oversized really.

 

[emf10]

For 2005 I think it would require 250kcm AL SE with 75 degree terminals since the 200A feed from the main breaker to a 200A panel in the house is not the "main power feeder" (from the poco to the 200A panel with the well breakers is the main feeder and could use #4/0 AL), for 2008 it would more clearly be #350kcm AL SE since it dosen't carry all loads associated with the dwelling and SE is restricted to the 60 degree column. Seems oversized really.

But since the service entrance conductors are likely #4/0 AL, they can be reduced to that size because they are not required to be larger than the service entrance conductors.

 

[Flex]

But since the service entrance conductors are likely #4/0 AL, they can be reduced to that size because they are not required to be larger than the service entrance conductors.

where does it say that. the power company almost always has smaller than 4/0 to the weatherhead.

 

[Dennis Alwon]

Try explaining that new conduit running accross some ladys living room ceiling....

I would tell her it looks better than se cable running across there.

 

[iwire]

where does it say that. the power company almost always has smaller than 4/0 to the weatherhead.

Forget about what the power company does those conductors between the pole and the weather head are not 'service conductors' to the NEC.

215.2(A)(2) is the section that says no feeder has to be larger then the NEC service conductors.

 

[Dennis Alwon]

For 2005 I think it would require 250kcm AL SE with 75 degree terminals since the 200A feed from the main breaker to a 200A panel in the house is not the "main power feeder" (from the poco to the 200A panel with the well breakers is the main feeder and could use #4/0 AL), for 2008 it would more clearly be #350kcm AL SE since it dosen't carry all loads associated with the dwelling and SE is restricted to the 60 degree column. Seems oversized really.

I disagree with the use of 250KCM. 250KCM is only good for 170 amps when used as a SE cable. You would need to use 300 kcm if the calculated load is under 190 otherwise you need 350 KCM.

But since the service entrance conductors are likely #4/0 AL, they can be reduced to that size because they are not required to be larger than the service entrance conductors.

I agree with this to a point. Since 4/0 is used as the service entrance conductor I still believe you are required to run a wire that is sized based on T. 310.16. Art. 215.2(A)(3) references P 310.15(B)(6) which allows the T310.15(B)(6) to be used when the feeder carries the entire load.

Here is the catch. What does larger mean? Does it mean larger in size or larger in ampacity. I believe it means larger ampacity not actual wire size. Here is why....

If we use 2/0 copper service conductors for a 200 amp service and feed thru to another panel that does not carry the entire load then I could use 2/0 aluminimum because it is not larger then the se conductors. WRONG, but that is what everyone wants to interpret 215.2(A)(3) as meaning. To me it obviously is talking about ampacity.

4/0 alum. from the meter to a house panel with other loads, IMO needs a minimum 300 KCM, and possibly 350 Kcm, to feed thru to a 200 amp panel protected by the main 200 amp breaker.

 

[LarryFine]

215.2(A)(2) is the section that says no feeder has to be larger then the NEC service conductors.

4/0 alum. from the meter to a house panel with other loads, IMO needs a minimum 300 KCM, and possibly 350 Kcm, to feed thru to a 200 amp panel protected by the main 200 amp breaker.

You can't both be correct.

 

[emf10]

I disagree with the use of 250KCM. 250KCM is only good for 170 amps when used as a SE cable. You would need to use 300 kcm if the calculated load is under 190 otherwise you need 350 KCM.

For 2005 SE was still permitted to use the 75 degree column which lists 250kcm AL SE as 205 amps.

Here is the catch. What does larger mean? Does it mean larger in size or larger in ampacity. I believe it means larger ampacity not actual wire size. Here is why....

If we use 2/0 copper service conductors for a 200 amp service and feed thru to another panel that does not carry the entire load then I could use 2/0 aluminimum because it is not larger then the se conductors. WRONG, but that is what everyone wants to interpret 215.2(A)(3) as meaning. To me it obviously is talking about ampacity.

4/0 alum. from the meter to a house panel with other loads, IMO needs a minimum 300 KCM, and possibly 350 Kcm, to feed thru to a 200 amp panel protected by the main 200 amp breaker.

You might be right. It does say it needs not have an ampacity rating greater than the service entrance conductors. The method used to rate the SE cable from the poco to the 200A well panel is different from the method used from the well panel to another panel. Either way they do use the term ampacity and not "larger" or "smaller", 310.15(b)(6). So I think 350kcm AL SE for the well panel to another 200A panel (using NEC 2008), unless there is an exception elsewhere in the code.

 

[iwire]

You can't both be correct.

LOL

I think we can be when the question we are trying to answer is not clear.

I think this whole thread is a train wreck, there are at least 3 different code sections being intermixed here.

• There is the change for SE temperature.
  
• There is the change that was not really a change in 310.15(b)(6)
  
• There is the poor wording in 215.2(A)(2)

 

[Dennis Alwon]

You can't both be correct.

You noticed that too..... Well, I am correct . Obviously as Bob stated the wording is iffy but my opinion may differ from Bob's. You take it for what it is worth. I know around our area art. 215.2(A)(2) will be interpreted as I explained it.

 

[Twoskinsoneman]

LOL

I think we can be when the question we are trying to answer is not clear.

I think this whole thread is a train wreck, there are at least 3 different code sections being intermixed here.

• There is the change for SE temperature.
  
• There is the change that was not really a change in 310.15(b)(6)
  
• There is the poor wording in 215.2(A)(2)

Maybe it's because these three sections (if I recall correctly) are written by different panels and they aren't communicating properly.

This is ridiculous! From now on all the code decisions need to be made by a single guy to keep it straight!!! I volunteer me!

 

[PetrosA]

215.2(A)(2) is the section that says no feeder has to be larger then the NEC service conductors.

I thought it talked about the ampacity of the conductors not having to be greater, which would allow a larger size wire at a lower temp calculation, or am I misunderstanding it?